A waterproof electronic control apparatus has been proposed, for example, in U.S. Pat. No. 6,707,678 corresponding to JP 2001-85858. In an electronic control apparatus proposed in U.S. Pat. No. 6,707,678, a circuit board and a connector mounted on the circuit board are accommodated in an inner space of a casing. The casing is sealed by a sealing material so that the inner space of the casing can be water-sealed.
Specifically, the electronic control apparatus includes a casing having a top opening in its upper face portion for accommodating the circuit board and a cover for covering the opening of the casing. A side wall of the casing has a connector opening joined to the top opening. The opening of the casing is covered with the cover. Thus, the circuit board is accommodated in the casing such that the connector mounted on the circuit board is partially exposed outside the casing through the connector opening. The sealing material is applied between a top opening edge of the casing and an outer edge of the cover, between an outer surface of the connector and the outer edge of the cover, and between a connector opening edge of the casing and the outer surface of the connector.
In such a waterproof electronic control apparatus, a sealing material is applied to either an edge of a casing or an edge of a cover at a constant speed to improve productivity (i.e., manufacturing efficiency) of the electronic control apparatus. The edge, to which the sealing material is applied, has a substantially rectangular ring shape with corners to follow the outer shape of the circuit board. If at least one of the corners forms a right angle, it is difficult to uniformly apply the sealing material to the ring-shaped edge at the constant speed. The speed needs to be changed between a straight portion and a corner portion of the ring-shaped edge. As a result, the productivity of the electronic control apparatus is reduced.
In the electronic control apparatus proposed in U.S. Pat. No. 6,707,678, the corners of the ring-shaped edge are rounded. In such an approach, the sealing material can be uniformly applied to the ring-shaped edge at the constant speed to prevent a reduction in productivity.
However, in the electronic control apparatus proposed in U.S. Pat. No. 6,707,678, a seal between the casing and the connector is formed using a middle portion of one side of the ring-shaped edge of the casing. Therefore, the size of the casing in a longitudinal direction of the connector depends on the sum of the longitudinal length of the connector, the length of end portions of the one side of the ring-shaped edge, and the size of adjacent two corners directly joined through the one side. For this reason, it is difficult to reduce the size of the casing and accordingly the size of the electronic control apparatus.